I think you need to try with a SNAPSHOT of 3.0. As I mentioned in a previous email 3.0 now longer generates a .dat file but generates a Java source file that gets compiled with your source code instead. It also requires a .service file for ServiceLoader but those should be handled out of the box by shading tools.
Ralph > On Aug 21, 2019, at 9:20 AM, Gregg Donovan <[email protected]> wrote: > > Hello! > > I'm working on getting Etsy's custom StackdriverJsonLayout Log4J plugin to > work with our Bazel-based build system and wanted to run a few ideas by you. > > The first problem I ran into was stdout messages breaking the > PluginProcessor annotation processor when run by Bazel. My PR here[1] fixed > that for us. > > The problem we have now is with "fat jars" and the plugin cache > file > (META-INF/org/apache/logging/log4j/core/config/plugins/Log4j2Plugins.dat)[2]. > When Bazel builds a "deploy" jar, it combines an application's classes and > the classes of its transitive dependencies into a single "fat" JAR. During > this process it needs to intelligently combine any duplicate JAR entries it > finds. > > Right now, Bazel does not know about the plugin cache file[3], so it keeps > the first one it encounters and discards any others. So, our custom > plugin's plugin cache file is discarded in the process.[4] > > Even if Bazel knew about the plugin cache file, I don't think the binary > format is easily concatenated, due to the length header. [5] > > I have a few suggestions for fixing this that I'd like to run by you all > before submitting a patch: > > Make the .dat files concatenateable, either textually (i.e. inserting a \n > between combined files) or as binary data (i.e. no inserted bytes). This > makes the job of the build tool much easier. > There seem to be two options: > a) Move from a binary format to textual (say, tab delimited PluginEntry > fields) and combine the dat files as plain text. > If this option is chosen, we could either teach Bazel's DefaultJarEntry > filter to combine the plugin cache file textually or move it into > META-INF/services, where all files are combined as textual data.[6] > > b) Remove the length header and allow the .dat files to be combined as > binary data. > If we choose this option, we would need to teach Bazel's > DefaultJarEntryFilter to combine the plugin cache file as binary, as it > does for proto files.[7] > > What do you think? Thanks for the consideration! > > Gregg > > [1]: https://github.com/apache/logging-log4j2/pull/301 > [2]: > https://github.com/apache/logging-log4j2/blob/cd87dd40405166a4d5f6707a27cbaf7ddcf833b6/log4j-plugins/src/main/java/org/apache/logging/log4j/plugins/processor/PluginProcessor.java#L67 > [3]: > https://github.com/bazelbuild/bazel/blob/master/src/java_tools/singlejar/java/com/google/devtools/build/singlejar/DefaultJarEntryFilter.java > [4]: > https://github.com/bazelbuild/bazel/blob/0d39361075b05919618720f961870d3863a726ac/src/java_tools/singlejar/java/com/google/devtools/build/singlejar/ZipEntryFilter.java#L87:L91 > [5]: > - > https://github.com/apache/logging-log4j2/blob/92d19c8da6591a706a2df9875c7e41f6fb20bd66/log4j-core/src/main/java/org/apache/logging/log4j/core/config/plugins/processor/PluginCache.java#L73 > - > https://github.com/apache/logging-log4j2/blob/92d19c8da6591a706a2df9875c7e41f6fb20bd66/log4j-core/src/main/java/org/apache/logging/log4j/core/config/plugins/processor/PluginCache.java#L101 > [6]: > https://github.com/bazelbuild/bazel/blob/447e0f1aedb1d83feba2298b1e251b4e34ed9a70/src/java_tools/singlejar/java/com/google/devtools/build/singlejar/DefaultJarEntryFilter.java#L99:L101 > [7]: > https://github.com/bazelbuild/bazel/blob/447e0f1aedb1d83feba2298b1e251b4e34ed9a70/src/java_tools/singlejar/java/com/google/devtools/build/singlejar/DefaultJarEntryFilter.java#L115:L117
